Uninterruptible power supply

ABSTRACT

A battery of an uninterruptible power supply unit  1   a  is configured by at least two batteries (a first battery  2  and a second battery  21   a ). A control circuit  12   a  judges opened/closed states of a first cover  6   a  and a second cover  25   a  on the basis of information from a first cover-opening detecting device  7   a  and a second cover-opening detecting device  11   a . When the first cover  6   a  is opened, a first switch  8  which connects a charge and discharge circuit  3  to the first battery  2  is opened, and, when the second cover  25   a  is opened, a second switch  10  which connects the charge and discharge circuit  3  to the second battery  21   a  is opened.

TECHNICAL FIELD

The present invention relates to an uninterruptible power supply unit which has a battery, and which normally supplies an electric power of an AC power source to a backed-up apparatus, and, when the AC power source is interrupted, supplies an electric power from the battery to the backed-up apparatus.

BACKGROUND ART

FIG. 4 is a view showing the configuration of a conventional uninterruptible power supply unit. In the figure, 40 denotes an AC power source, 41 a denotes an uninterruptible power supply unit, and 42 denotes a backed-up apparatus such as a computer system which, when the AC power source 40 is interrupted, is to be backed up by the uninterruptible power supply unit 41 a. Furthermore, 50 denotes a battery which is incorporated in the uninterruptible power supply unit 41 a, 51 denotes a charge and discharge circuit which, when the AC power source 40 is in the normal state, causes the battery 50 to be charged by the AC power source 40, and which, when the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, causes the battery 50 to be discharged, thereby supplying an electric power to the backed-up apparatus 42, and 52 denotes a connector trough which the battery 50 and the charge and discharge circuit 51 are connected to each other. Furthermore, 53 a denotes a case of the uninterruptible power supply unit 41 a housing the battery 50, 54 denotes an opening which is used for replacement of the battery 50, 55 a denotes a cover for closing the opening 54, 56 denotes a cover-opening detecting device which detects an opened/closed state of the cover 55 a by using an optical switch or the like, and 57 denotes a charge and discharge circuit disconnecting switch which disconnects the charge and discharge circuit 52 from the AC power source 40.

When the AC power source 40 is normal, the uninterruptible power supply unit 41 a supplies an electric power from the AC power source 40 to the backed-up apparatus 42, and closes the charge and discharge circuit disconnecting switch 57 to connect the AC power source 40 to the charge and discharge circuit 51 to charge the battery 50. When the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, the uninterruptible power supply unit 41 a serves as a backup power source to discharge the battery 50 to supply an electric power to the backed-up apparatus 42. The battery 50 is repeatedly rechargable, but its power suppliable time is shortened as a result of aging. Therefore, the battery is usually replaced with a fresh one at two- or three-year intervals.

The uninterruptible power supply unit 41 a detects the opened/closed state of the cover 55 a by means of the cover-opening detecting device 56. When the cover 55 a is opened, the unit judges that replacement of the battery 50 is to be performed, and then opens the charge and discharge circuit disconnecting switch 57 to disconnect the charge and discharge circuit 51 from the AC power source 40. As a result, it is possible to prevent replacement of the battery 50 from being performed during a charging process in which a charging current flows through the battery 50.

FIG. 5 is a view showing the configuration of a conventional uninterruptible power supply unit. A battery which is to be separately placed is additionally disposed. In the figure, 40, 42, 50 to 52, 54, and 57 denote the identical components as those of FIG. 4, and their description is omitted. Furthermore, 41 b denotes an uninterruptible power supply unit, 53 b denotes a case of the uninterruptible power supply unit 41 b housing the battery 50, 55 b denotes a cover for closing the opening 54, 58 denotes a battery replacement instruction switch which closes and opens the charge and discharge circuit disconnecting switch 57, 60 denotes a battery unit which is placed separately from the uninterruptible power supply unit 41 b, 61 denotes an auxiliary battery which is incorporated in the battery unit 60, and which is connected in parallel to the battery 50, and 62 denotes a connector to which the auxiliary battery 61 is connected.

The uninterruptible power supply unit 41 a of FIG. 4 is an example in which only the battery 50 incorporated in the uninterruptible power supply unit 41 a is used as a battery. The uninterruptible power supply unit 41 b of FIG. 5 is an example in which, in order to prolong the backup time, the battery unit 60 in which the auxiliary battery 61 is incorporated is additionally disposed so that a battery is configured by the battery 50 and the auxiliary battery 61.

When the AC power source 40 is normal, the uninterruptible power supply unit 41 b supplies an electric power from the AC power source 40 to the backed-up apparatus 42, and closes the charge and discharge circuit disconnecting switch 57 to connect the AC power source 40 to the charge and discharge circuit 51 to charge the batteries (the battery 50 and the auxiliary battery 61). When the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, the uninterruptible power supply unit 41 b serves as a backup power source to discharge the batteries (the battery 50 and the auxiliary battery 61) to supply an electric power to the backed-up apparatus 42.

In replacement of the batteries (the battery 50 and the auxiliary battery 61) in the uninterruptible power supply unit 41 b, when the battery 50 incorporated in the uninterruptible power supply unit 41 b is to be replaced, the cover 55 b is opened. By contrast, when the auxiliary battery 61 incorporated in the battery unit 60 which is placed separately from the uninterruptible power supply unit 41 b is to be replaced, the cover 55 b is not opened. Therefore, the battery replacement instruction switch 58 is disposed so that, when the batteries (the battery 50 and the auxiliary battery 61) are to be replaced, the battery replacement instruction switch 58 is operated. When the battery replacement instruction switch 58 is operated, it is judged that instructions for the battery replacement has been given, and the charge and discharge circuit disconnecting switch 57 is then opened to disconnect the charge and discharge circuit 51 from the AC power source 40.

In replacement of the battery of the uninterruptible power supply unit, as described above, the charge and discharge circuit disconnecting switch 57 is opened in response to an operation of the cover-opening detecting device 56 or the battery replacement instruction switch 58, so that the battery replacement is prevented from being performed during a charging process. However, there is a problem in that, when power interruption or momentary power interruption occurs during a process of replacing the battery, it is impossible to exert the original function of an uninterruptible power supply unit that, in the case of power interruption, the unit supplies an electric power to a backed-up apparatus.

The invention has been conducted in order to solve the above-discussed problem. It is an object of the invention to obtain an uninterruptible power supply unit which, even when power interruption or momentary power interruption occurs during a process of replacing a battery, can supply an electric power to a backed-up apparatus.

DISCLOSURE OF THE INVENTION

The uninterruptible power supply unit of the invention is an uninterruptible power supply unit which has a battery and a charge and discharge circuit, and in which, when an AC power source is in a normal state, the AC power source is used as a power source to supply an electric power to a backed-up apparatus, and the battery is charged by the charge and discharge circuit, and, when the AC power source is in an abnormal state such as power interruption, the battery is discharged by the charge and discharge circuit to supply an electric power to the backed-up apparatus, wherein the battery is configured by a first battery and a second battery, the unit comprises: a first switch which connects the charge and discharge circuit to the first battery; a second switch which connects the charge and discharge circuit to the second battery; a first cover which is opened when the first battery is to be replaced; a second cover which is opened when the second battery is to be replaced; a first cover-opening detecting device which detects an opened state of the first cover; a second cover-opening detecting device which detects an opened state of the second cover; and a control circuit which controls opening/closing of the first switch and the second switch in accordance with opened/closed states of the first cover and the second cover, when the first cover is opened, the first switch is opened to enable replacement of the first battery, and, when the second cover is opened, the second switch is opened to enable replacement of the second battery.

Furthermore, the second battery, the second cover, the second cover-opening detecting device, and the second switch constitute a battery unit which can be disposed separately from the uninterruptible power supply unit, and which is connected to the charge and discharge circuit through a connector.

Moreover, the uninterruptible power supply unit has at least one of a display device and an alarm device, and, when the first cover or the second cover is opened, the control circuit gives an alarm for an opened state of the cover.

Furthermore, the first cover or the second cover comprises interlocking means, and the control circuit interlocks the second cover when the first cover is opened, and interlocks the first cover when the second cover is opened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 1 of the invention which comprises a first battery and a second battery.

FIG. 2 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 2 of the invention which comprises: a display device that displays an error message indicative of a cover opened state; an alarm outputting section that gives an alarm for the cover opened state; and interlocking means for, when one cover is opened, interlocking another cover.

FIG. 3 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 3 of the invention in which a first battery unit and a second battery unit are disposed outside the uninterruptible power supply unit.

FIG. 4 is a view showing the configuration of a conventional uninterruptible power supply unit.

FIG. 5 is a view showing the configuration of a conventional uninterruptible power supply unit in which a battery that is to be separately placed is additionally disposed.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1

FIG. 1 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 1 of the invention which comprises a first battery and a second battery. In the figure, 1 a denotes the uninterruptible power supply unit, 2 denotes the first battery, and 3 denotes a charge and discharge circuit which, when an AC power source 40 is in the normal state, causes the first battery 2 and a second battery 21 a that will be described later to be charged by the AC power source 40, and which, when the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, causes the first battery 2 and the second battery 21 a that will be described later to be discharged, thereby supplying an electric power to a backed-up apparatus 42. Furthermore, 4 a denotes a case of the uninterruptible power supply unit 41 a which houses the first battery 2, 5 a denotes an opening of the case 4 a which is used for replacement of the first battery 2, 6 a denotes a first cover for closing the opening 5 a, 7 a denotes a first cover-opening detecting device which detects an opened/closed state of the first cover 6 a, 8 denotes a first switch which closes and opens the connection between the charge and discharge circuit 3 and the first battery 2, 9 denotes a first connector trough which the first battery 2 and the first switch 8 are connected to each other, 10 denotes a second switch which closes and opens the connection between the charge and discharge circuit 3 and the second battery 21 a that will be described later, 11 a denotes a second cover-opening detecting device which detects an opened/closed state of a second cover 25 a that will be described later, and 12 a denotes a control circuit which controls opening/closing of the first switch 8 and the second switch 10 in accordance with the opened/closed states of the first cover 6 a and the second cover 25 a.

Furthermore, 20 a denotes a battery unit which is disposed outside the uninterruptible power supply unit 1 a, 21 a denotes the second battery which is incorporated in the battery unit 20 a, and 22 denotes a second connector for connecting the second battery 21 a. Furthermore, 23 a denotes a case which houses the second battery 21 a, 24 a denotes an opening of the case 23 a which is used for replacement of the second battery 21 a, 25 a denotes a second cover for closing the opening 24 a, and 26 denotes an operation piece which is disposed on the second cover 25 a. Furthermore, 27 a denotes a second cover open/close switch which is closed or opened by the operation piece 26 when the second cover 25 a is opened or closed, and 28 denotes a second cover opened/closed state detection resistor which is connected in parallel to the second cover open/close switch 27 a.

When the second cover 25 a of the battery unit 20 a is opened, the operation piece 26 which has caused the second cover open/close switch 27 a to be opened is disengaged from the switch to close the second cover open/close switch 27 a. The second cover-opening detecting device 11 a detects the value of the second cover opened/closed state detection resistor 28 which is connected in parallel to the second cover open/close switch 27 a, and, when the second cover open/close switch 27 a is closed and a resistance of 0 Ω is detected as a result of formation of a closed circuit of the switch and the second cover opened/closed state detection resistor 28, judges that the second cover 25 a of the battery unit 20 a is opened.

From information given from the first cover-opening detecting device 7 a and the second cover-opening detecting device 11 a, the control circuit 12 a judges the opened/closed states of the first cover 6 a and the second cover 25 a, so that, when the first cover 6 a is opened, the circuit opens the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, and, when the second switch 25 a is opened, opens the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a.

When the AC power source 40 is normal, the uninterruptible power supply unit 1 a supplies an electric power to the backed-up apparatus 42, and closes the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, and the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a, so that the batteries (the first battery 2 and the second battery 21 a) are charged by the charge and discharge circuit 3. When the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, the uninterruptible power supply unit 1 a serves as a backup power source to discharge the batteries (the first battery 2 and the second battery 21 a), thereby supplying an electric power to the backed-up apparatus 42.

When the first cover 6 a is opened, the control circuit 12 a opens the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, to enable replacement of the first battery 2. In this case, the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a is closed, and hence the unit is effective as a backup power source. When the second cover 25 a is opened, the control circuit 12 a opens the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a, to enable replacement of the second battery 21 a. In this case, the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2 is closed, and hence the unit is effective as a backup power source.

As described above, in Embodiment 1, the battery of the uninterruptible power supply unit is configured by at least two batteries, and a battery which is to be replaced is individually isolated. Therefore, replacement of the battery can be safely performed, and, even when power interruption or momentary power interruption occurs during a process of replacing the battery, the uninterruptible power supply unit can serve as a backup power source to supply an electric power to a backed-up apparatus.

Embodiment 2

FIG. 2 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 2 of the invention which comprises: a display device that displays an error message indicative of a cover opened state; an alarm outputting section that gives an alarm for the cover opened state; and interlocking means for, when one cover is opened, interlocking another cover. In the figure, 2, 3, 7 a, 8 to 10, 21 a, 22, 26, 27 a, 28, 40, and 42 denote the identical components as those of FIG. 1, and their description is omitted. Furthermore, 1 b denotes the uninterruptible power supply unit, 4 b denotes a case of the uninterruptible power supply unit 1 b which houses the first battery 2, 5 b denotes an opening which is used for replacement of the first battery 2, 6 b denotes a cover for closing the opening 5 b, 11 b denotes a second cover-opening detecting device which detects an opened/closed state of the second cover 25 b that will be described later, and 12 b denotes a control circuit which, in accordance with the opened/closed states of the first cover 6 b and the second cover 25 b, controls opening/closing of the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, and that of the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a.

Furthermore, 20 b denotes a battery unit which is disposed outside the uninterruptible power supply unit 1 b, 23 b denotes a case which houses the second battery 21 a, 24 b denotes an opening which is used for replacement of the second battery 21 a, and 25 b denotes a second cover for closing the opening 24 b.

Furthermore, 30 denotes the display device which, when the first cover 6 b or the second cover 25 b is opened, displays an error message indicative of a cover opened state, and 31 denotes the alarm outputting section which, when the first cover 6 b or the second cover 25 b is opened, gives an alarm for the cover opened state. Furthermore, 32 denotes a first cover interlocking section which interlocks the opening 5 b and the first cover 6 b of the uninterruptible power supply unit 1 b, and 33 denotes a second cover interlocking section which interlocks the second opening 24 b and the second cover 25 b.

When the first cover 6 b is opened, the control circuit 12 b opens the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, to enable replacement of the first battery 2, and gives an output indicative of a cover opened state to the display device 30 and the alarm outputting section 31. In this case, the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a is closed, and hence the unit is effective as a backup power source. When the first cover 6 b is opened, the second cover 25 b is interlocked by the second interlocking section 33. When the second cover 25 b is opened, the control circuit 12 b opens the second switch 10 which connects the charge and discharge circuit 3 to the second battery 21 a, to enable replacement of the second battery 21 a, and gives an output indicative of a cover opened state to the display device 20 and the alarm outputting section 21 a. In this case, the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2 is closed, and hence the unit is effective as a backup power source. When the second cover 25 b is opened, the first cover 6 b is interlocked by the second interlocking section 32.

As described above, in Embodiment 2, when the cover 6 b of the uninterruptible power supply unit 1 b in which the first battery 2 is incorporated is opened, the second cover 25 b of the battery unit 20 b in which the second battery 21 a is incorporated is interlocked, and, when the second cover 25 b of the battery unit 20 b in which the second battery 21 a is incorporated is opened, the cover 6 b of the uninterruptible power supply unit 1 b in which the first battery 2 is incorporated is interlocked. Therefore, the battery replacement can be performed in a state where one of the batteries (the first battery 2 and the second battery 21 a) of the uninterruptible power supply unit is surely connected. Even when a power source failure such as power interruption or momentary power interruption occurs during a process of replacing the battery, therefore, the unit can serve as a backup source to supply an electric power to the backed-up apparatus.

When the cover 6 b of the uninterruptible power supply unit 1 b or the second cover 25 b of the battery unit 20 b is opened, the display device 30 displays an error message indicative of the cover opened state, and the alarm outputting section 31 produces an alarm output of the cover opened state. Therefore, the operator can know that one of the batteries (the first battery 2 and the second battery 21 a) is insulated and the power suppliable time is shortened.

In FIG. 2 described above, the example which comprises the unit comprises both the display device 30 that displays an error message indicative of a cover opened state, and the alarm outputting section 31 that gives an alarm for the cover opened state has been described. Alternatively, the unit may comprise only one of the device and the section.

Embodiment 3

FIG. 3 is a view showing the configuration of an uninterruptible power supply unit of Embodiment 3 of the invention in which a first battery unit and a second battery unit are disposed outside the uninterruptible power supply unit. In the figure, 2, 3, 7 a, 22, 26, 40, and 42 denote the identical components as those of FIG. 1, and their description is omitted. Furthermore, 1 c denotes the uninterruptible power supply unit, 4 c denotes a case of the uninterruptible power supply unit 1 c which houses the first battery 2, 5 c denotes an opening of the case 4 c which is used for replacement of the first battery 2, 6 c denotes a first cover for closing the opening 5 c, and 12 c denotes a control circuit which, in accordance with the opened/closed states of the first cover 5 c, and a second cover 25 c and a third cover 25 d that will be described later, controls opening/closing of a first switch 8 that connects the charge and discharge circuit 3 to the first battery 2, that of a second switch 34 a that will be described later, and that connects the charge and discharge circuit 3 to a second battery 21 a which will be described later, and that of a third switch 34 b that will be described later, and that connects the charge and discharge circuit 3 to a third battery 21 b which will be described later.

Furthermore, 20 c denotes a first battery unit which is disposed outside the uninterruptible power supply unit 1 c, 20 d denotes a second battery unit which is disposed outside the uninterruptible power supply unit 1 c, 21 a denotes the second battery, 21 b denotes the third battery, 23 c denotes a case which houses the second battery 21 a, 23 d denotes a case which houses the third battery 21 b, 24 c denotes an opening of the case 23 c which is used for replacement of the second battery 21 a, 24 d denotes an opening of the case 23 d which is used for replacement of the third battery 21 b, 25 c denotes a second cover for closing the opening 24 c, 25 d denotes a third protective cover for closing the opening 24 d, 27 a denotes a second cover open/close switch which is closed or opened by the operation piece 26 when the second cover 25 c is opened or closed, 27 b denotes a third cover open/close switch which is closed or opened by the operation piece 26 when the third cover 25 d is opened or closed, 34 a denotes a second switch which connects the charge and discharge circuit 3 to the second battery 21 a, 34 b denotes a third switch which connects the charge and discharge circuit 3 to the third battery 21 b, 35 a denotes a second cover opened/closed state detection resistor which is connected in parallel to the second cover open/close switch 27 a, 35 b denotes a third cover opened/closed state detection resistor which is connected in parallel to the third cover open/close switch 27 b, 36 a denotes a second cover-opening detecting device which detects an opened/closed state of the second cover 25 c, and 36 b denotes a third cover-opening detecting device which detects an opened/closed state of the third cover 25 d.

In the first battery unit 20 c, when the second cover 25 c is opened, the operation piece 26 which has caused the second cover open/close switch 27 a to be opened is disengaged from the switch to close the second cover open/close switch 27 a. The second cover-opening detecting device 36 a detects the value of the second cover opened/closed state detection resistor 35 a, and, when the second cover open/close switch 27 a is closed and a resistance of 0 Ω is detected as a result of formation of a closed circuit of the switch and the second cover opened/closed state detection resistor 35 a, judges that the second cover 25 c is opened.

In the second battery unit 20 d, similarly, when the third cover 25 d is opened, the operation piece 26 which has caused the third cover open/close switch 27 b to be opened is disengaged from the switch to close the third cover open/close switch 27 b. The third cover-opening detecting device 36 b detects the value of the third cover opened/closed state detection resistor 35 b, and, when the third cover open/close switch 27 b is closed and a resistance of 0 Ω is detected as a result of formation of a closed circuit of the switch and the third cover opened/closed state detection resistor 35 b, judges that the third cover 25 d is opened. FIG. 3 shows an example in which the third cover 25 d is opened and the third cover open/close switch 27 b is closed.

From information given from the first cover-opening detecting device 7 a, the second cover-opening detecting device 36 a, and the third cover-opening detecting device 36 b, the control circuit 12 c judges the opened/closed states of the first cover 6 c, the second cover 25 c, and the third cover 25 d, so as to control opening/closing of the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, that of the second switch 34 a which connects the charge and discharge circuit 3 to the second battery 21 a, and that of the third switch 34 b which connects the charge and discharge circuit 3 to the third battery 21 b.

When the AC power source 40 is normal, the uninterruptible power supply unit 1 c supplies an electric power to the backed-up apparatus 42, and closes the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, the second switch 34 a which connects the charge and discharge circuit 3 to the second battery 21 a, and the third switch 34 b which connects the charge and discharge circuit 3 to the third battery 21 b, so that the batteries (the first battery 2, the second battery 21 a, and the third battery 21 b) are charged by the charge and discharge circuit 3. When the AC power source 40 is in an abnormal state such as power interruption or momentary power interruption, the uninterruptible power supply unit 1 c serves as a backup power source to discharge the batteries (the first battery 2, the second battery 21 a, and the third battery 21 b), thereby supplying an electric power to the backed-up apparatus 42.

During a process of replacing the batteries (the first battery 2, the second battery 21 a, and the third battery 21 b), when the first cover 6 a is opened, the control circuit 12 c opens the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, to enable replacement of the first battery 2. In this case, the second switch 34 a which connects the charge and discharge circuit 3 to the second battery 21 a, and the third switch 34 b which connects the charge and discharge circuit 3 to the third battery 21 b are closed, and hence the unit is effective as a backup power source. When the second cover 25 c (or the third cover 25 d) is opened, similarly, the control circuit 12 c opens the second switch 34 a which connects the charge and discharge circuit 3 to the second battery 21 a (or the third switch 34 b which connects the charge and discharge circuit 3 to the third battery 21 b), to enable replacement of the second battery 21 a (or the third battery 21 b) In this case, the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, and the third switch 34 b which connects the charge and discharge circuit 3 to the third battery 21 b (or the first switch 8 which connects the charge and discharge circuit 3 to the first battery 2, and the second switch 34 a which connects the charge and discharge circuit 3 to the second battery 21 a) are closed, and hence the unit is effective as a backup power source.

In Embodiment 1, the example has been shown in which the uninterruptible power supply unit 1 a comprises: the second cover opened/closed state detection resistor 28 which is connected in parallel to the second cover open/close switch 27 a; and the second cover-opening detecting device 11 a which detects the value of the second cover opened/closed state detection resistor 28 to judge whether the second cover 25 a is opened or not. By contrast, in Embodiment 3, the battery unit 20 c (or the battery unit 20 d) comprises: the second cover opened/closed state detection resistor 35 a (or the third cover opened/closed state detection resistor 35 b) which is connected in parallel to the second cover open/close switch 27 a (or the third cover open/close switch 27 b); and the second cover-opening detecting device 36 a (or the third cover-opening detecting device 36 b) which detects the value of the second cover opened/closed state detection resistor 35 a (or the third cover opened/closed state detection resistor 35 b) to judge whether the second cover 25 c (or the third cover 35 d) is opened or not.

In Embodiment 3, the cover-opening detecting device is disposed in the battery unit which is disposed outside the uninterruptible power supply unit, a result of the cover opening detection is transmitted to the uninterruptible power supply unit, and opening/closing of the switch which connects the charge and discharge circuit to the battery is controlled. Even when a plurality of battery units are connected, therefore, battery replacement can be performed independently for each of the battery units.

In Embodiment 3 described above, the example in which two battery units, i.e., the first battery unit 20 c and the second battery unit 20 d are connected to the uninterruptible power supply unit 1 c has been shown. Alternatively, the first battery unit 20 c may be usually connected, and, when the battery is to be replaced, the second battery unit 20 d may be additionally connected in order to ensure the backup time during a process of replacing the battery.

Industrial Applicability

As described above, the uninterruptible power supply unit of the invention is suitably used a backup power source for an apparatus such as a computer which always requires a stabilized electric power even during a process of replacing a battery. 

What is claimed is:
 1. An uninterruptible power supply unit which has a battery and a charge and discharge circuit, and in which, when an AC power source is in a normal state, the AC power source is used as a power source to supply an electric power to a backed-up apparatus, and said battery is charged by said charge and discharge circuit, and, when the AC power source is in an abnormal state such as power interruption, said battery is discharged by said charge and discharge circuit to supply an electric power to the backed-up apparatus, characterized in that said battery is configured by a first battery and a second battery, said unit comprises: a first switch which connects said charge and discharge circuit to said first battery; a second switch which connects said charge and discharge circuit to said second battery; a first cover which is opened when said first battery is to be replaced; a second cover which is opened when said second battery is to be replaced; a first cover-opening detecting device which detects an opened state of said first cover; a second cover-opening detecting device which detects an opened state of said second cover; and a control circuit which controls opening/closing of said first switch and said second switch in accordance with opened/closed states of said first cover and said second cover; wherein when said first cover is opened, said first switch is opened to enable replacement of said first battery, and, when said second cover is opened, said second switch is opened to enable replacement of said second battery.
 2. An uninterruptible power supply unit according to claim 1, characterized in that said second battery, said second cover, said second cover-opening detecting device, and said second switch constitute a battery unit which can be disposed separately from said uninterruptible power supply unit.
 3. An uninterruptible power supply unit according to claim 1 or 2, characterized in that said unit has at least one of a display device and an alarm device, and, when said first cover or said second cover is opened, said control circuit gives an alarm for an opened state of said cover.
 4. An uninterruptible power supply unit according to any one of claims 1 to 3, characterized in that said first cover or said second cover comprises interlocking means, and said control circuit interlocks said second cover when said first cover is opened, and interlocks said first cover when said second cover is opened. 